The clypeus of the bee is the area below the antennae, but above the labrum and the mouth. In one of the bees above, it’s yellow in color compared to the rest of the face. The clypeus is one of the ways a bee can be identified, based on its shape as well as the type of hairs present on it.
Bees such as Osmia lignaria (Pictured above) use their clypei to build nests in naturally occurring holes or gaps, building small pockets inside for each of their eggs.
Bees can also use their face to collect pollen, rubbing it against flowers and then using their legs to collect the pollen that gets caught on their clypeus. These bees tend to have longer hairs to hold onto the pollen, such as Osmia inspergens (Pictured above).
The clypeus is especially useful in a practice known as buzz-pollination, where the bee vibrates against a flower whose pollen is not accessible to make the pollen shoot out and cover the bee. The pollen is caught on the bristles of the clypeus, so it can be collected and brought back to the hive.
This information is also available from the University of Calgary Invertebrate collection, where it was curated as part of a study on design inspired by bees.Edit Summary
“Many kinds of bees, both oligolectic and polylectic, obtain pollen from such flowers by vibrating (sonicating) them, the anther aperture usually directed toward the bee. Pollen shoots out and some of it clings to the bee, after which it can be handled in the usual way. The vibrating, caused by the wing muscles, results in bursts of audible sound, hence “buzz-pollination.” A review is by Buchmann (in Jones and Little, 1983). Müller (1996a) records buzzing during pollen collecting from Lamiaceae by bees with bristles on the frons (Rophites) or clypeus.” Michener 2007:20